Coarse Sharpie Test

The Coarse Sharpie test is used on new tile tools to tell when the tool has the same shape as the mirror. Once you have made the tool and it is very dry you mark each of the tiles with an X, as shown. You then proceed grinding with #120 and as the tiles come in contact with the glass the X's will be ground away. If your tiles have glaze on them you may also watch the glaze dissapear.